Booster pump for aircraft fuel systems



Aug- 11,1942. R. R. CURTIS I r 2,292,993 BOOSTBRPUMP FOR AIRCRAFT FUEL SYSTEMS I Filed Aug, 10, 1940 2 Sheets-Sheet l Puma/.1. A? Cue r/s Aug. "11, 1.942. RR. CURTIS 2,2929% BOOSTER PUMP FOR AIRCRAFT FUEL SYSTEMS "Filed Aug. 10, 1940 2 Sheets -Sheet 2 1905.55 )9. Cu/er/a Patented Aug. 11,1942

a BOOSTERPUMPFORAIRCRAFTFUEL l t SYSTEMS 1 Russell RL CurtisaDayton, Ohio, assignor to Curtis Pump Company,

ration of Ohio Dayton, Ohio, a corpo- Imus still-@1946 Application A ugust 10, 1941), Serial No. 352,064 uu (01. ins-113) x u u -14 Claims. IThis invention relates; to high altitudefuel systems for aircraft and particularly to a booster pump for use in connection therewith.

. In the operation of aircraft with gasoline as the fuel, it is well known that, as ,theatmospheric pressure drops with increase in altitude, a point the tank for delivery intothe suctionline tr the engine pump. t

It is therefore an object of this invention to:

further increase the altitude range of aircraft,

is finally reached where air and fixed gases in solution start to evolve and lighter constituents in the fuel to vaporize, until the engine fuel pump is no longer capableoI delivering. fuel in afully liquid form to the engine. This condition fre quently gives rise to what is known .inthe art as vapor lock." The agitation'of the fuel by the engine pump serves to aggravate the dim culties that may be experienced by accelerating the separationof the air, or other fixed gases, or

vapors from the liquid fuel. Where, as is usual lnlaircraft design,fthe fuel tank isconsiderably below the level of the engine and its carburetor, thepressure at the inletside of the engine fuel pump drops still lower than the atmospheric pressureon the fuel in thetank, due to the suction head at the enginepump inlet.

Even where the amount of elevation ofthe enthe suction line is usuallyof considerable length and-due to weight restrictions, of small diameter, sothat a considerable equivalent suction head is created at the inlet side of the engine pump. p The result of the foregoing conditionsis that the fuel starts breaking into vapor at theengine pump inlet at considerably lower altitude than it does in the fuel tank,and much inventive effort has beenexpended, in attempts to overcome this dimculty. In the specification of my copending applicaby so designing the booster pump and so arranging it with respect to the fuel tank, that fully liquid fuel may be drawn from the tank considerably above the altitude atwhichthe fuel has begun boiling in the tank. i

Other objects and advantages will become'evident as the invention is Iurther described with reference to the drawings, wherein,

Fig. 1 is an elevational view, partly in vertical section, of a booster pump and motor with a fragmentary portion of the fuel tank, all constructed and arranged in accordance withthis' invention. p u Fig. 2 is a top planview of the booster pump unit removed from the tank.

Fig. 3 is avariantform of thearrangement of the booster pump with thetank.

f Like numerals refer to like parts throughout gine above the fuel tank is of little consequence, 125

tion, Serial No. 324,658, flledMarch I8, 1940, it, is

proposed to employ a booster "pump, placed anywhere below the hydraulicgradient in the suction line, with means to bringit into action to raise the pressure in the suction line before an altitude has been reached where the fuel would ordinarily v p p l t t t a pump,- is substantially conventional, having a field.

boilat the engine pump inlet, u

But while this additionof a booster pump arrangement to'the fuel system, materially increases the altitude range, byboosting the pressure 7 the pump casing 10 and contains aseal, not

at the suctionfinlet of the engine pump where the pressuredrop is greatestso thatthe .engine pump may deliver unbroken liquid fuelto the enginatit is obvious that, if the craft is taken to still higher altitudes, a pointwill ultimately be the drawings.

The booster pump is 'of j the centrifugal type "comprising a pump casing It, provided internally with a volute l2 which does not differ materially from those of common practice. A throat member I4 covers the open side of the volute and is held to the casing by the screws l 6;

The impeller comprises a hub 20, a flange 22 and a series of curved vanes 24. The impeller is secured to the motor shaft 26 by the key 28 and nut3ll. I K

As illustrated in Fig. 1, a mounting ring 32 is secured to the inside of the lower wall 01 the tank 33, preferably bywelding orsimilar means. The ring 32 is blind tapped atcircumferentially spaced intervals for the screws 34 which extend through the flange 36, of the pump casing and secure the pump to the tank. A gasket 38 be tween the flange and tank, seals against leakage.

The electric motor 40, which operates the ring, 42 held between heads 44 and by nuts 48. The upperhead 46 is an integral portion of shown, to prevent leakage from the pump into themotor. One of the drain plugsbll, most conveniently located for a, particularinstallation,

may be removed and a drain pip inserted to reached where the fuel will start breaking up in the fuel tank itself and the booster pump will have difficulty in drawing iully liquefied fuel from .55

dispose of any leakage which may, occur.

Thus far the centrifugal pump described does not differ materially from the conventional, but certain'parts now to be described are particubeing substantially flush fuel. The fuel is ther from the tank and larly designed and positioned with respect to the tank to achieve a novel result.

In common practice, the diameter of the throat 52 of the member I! is usually made the same as the diameter of the circle representing the inner ends of the vanes 24, but in the'pump herein shown the circle defined by the constricted opening of the throat 52 overlies the vanes about midway of their lengths. Otherwise expressed, the circle defined by the throat opening is concentric with and lies intermediate the circles defined by the inner and outer ends of the vanes, respectively.

The inner halves of the vanes 24 which are exposed when viewed from above, as in Fig. 2, through the throat 52, are beveled off as at 54, Figs. 1 and 3, and the throat itself flares upwardly as at 56, the upper end of the flared part with the inside of the tank. The convergency of the throat wall 56 and the taper of the beveled edges 54 of the vanes form approximate continuations of each other.

The result of this special structure and arrangement is that there is created, immediately above the throat, a funnel-shaped whirlpool of the fuel, the particles of which rotate in the same direction as the impeller and move in corkscrew fashion toward it. This whirlpool extends well upward into the tank and is present as soon as the booster pump is put intov operation,

When an altitude is reached where the fuel in the tank starts breaking up, scattered bubbles 58 will first appear throughout the tank. However, as the fuel and bubble mixture approaches the impeller, the bubbles are thrown outwardly along the tapered surface 56 of the throat member 52 and flow upwardly in the tank as indicated by the arrows in a path shown at 60. Upon approaching the surface of the fuel in the tank the bubble-path widens out and the bubbles become larger until they burst at the surface of the thus freed from the air and gases and circulates as indicated by the arrows down through the whirlpool as a substantially solid or fully liquid feed 62 to the impeller.

As a result a countercurrent circulation of fuel and bubbles is created in the tank with the bubbles rising through the fuel outwardly from the whirlpool and with fully liquid fuel being fed down through the funnel-shaped whirlpool to the impeller. The fully liquid fuel is then thrown by centrifugal force between the vanes on the impeller and the throat member where the last remaining bubbles are forced from the fuel outwardly along the path indicated at 60.

From the foregoing description it will be seen that, equipped with a booster pump of the character disclosed, aircraft may be flown to considerably higher altitudes than has heretofore been possible, for the reason that even after considerable vaporization is taking place in the fuel tank. evidenced by bubbles of vapor appearing throughout the mass, these bubbles may be separated out, and fuel in a fully liquid state put under pressure in the suction line of the engine pump.

If the throat of the booster pump were of con-' ventional design, or if the pump were spaced furfuel were conveyed to the vanes through a conduit of some considerable length and of unvarying diameter, or if the vane and throat proportions were conventional, vapor bubbles appearing in the fuel would be trapped and sent into the engine pump suction line in penditure of additional energy tation is vital to successful altitude performance ever increasing quantities until vapor lock occurred.

In some instances, space limitations are such that the booster pump unit may not be secured to the bottom of the tank as in Fig. 1, and in such cases, the pump may be mounted as in Fig. 3, on a normally vertical end wall of the tank, by providing a sump 64 with an opening in the end wall near the bottom of the sump. The whirlpool 62 and its vortex 60 will, in this case, have a somewhat curved axis, but it has been found that separation of the vapor from the solid fuel will be almost as effective in this case as in that previously described.

The pump unit is the same in both embodiments, only its position relative to the tank is different. It should be noted, however, that in both cases, the throat of the pump is comparatively shallow and opens directly into a large mass of fuel in the tank, thus lending itself to the centrifugal separation of the bubbles of gas or vapor from the mass of liquid fuel with minimum danger of entrapping the bubbles and drawing them into the impeller.

The construction and design of the booster pump of my present invention departs from conventional centrifugal pump practice and accepts a consequent loss in efilciency in order to achieve a certain result.

The separation characteristic inherent in centrifugal pumps has been emphasized to force separation of dissolved air and fixed gases and vapor before these gases can be entrapped and passed through the pump. To accomplish this I have found it necessary to greatly reduce the throat velocity over that which is normally provided for. by increasing the inlet throat diameter and bevelling it outwardly toward the tank. As no advantage is taken of the velocity of incoming fluid, and as an abrupt change in velocity takes place as fluid reaches the impeller, efficiency is considerably lowered.

To build up a greater vortex requires the exbut increased agiof this system. So the impeller vanes have been extended in toward thecenter of the impeller beyond the throat diameter to produce this result.

The booster described has two functions: the first to separate out bubbles of gas which form at the inlet, due to agitation of the liquid, and elsewhere in the tank; and the second to exert pressure on the engine pump suction line and prevent a further evolution of gas which might otherwise take place in the suction inlet line or in the engine pump as the fuel is further agitated.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. In a booster pump of the character described, a pump casing, an impeller, vanes on and radiating outwardly from the rotating axis of said impeller, and a member having a conical shaped inlet throat concentric with the axis of said impeller and its side of said vanes, said throat being of a diameter intermediate the outside and inside diameters of the vanes, and said vanes being beveled from a point intermediate their ends inward,

tapered end adjacent one.

of saidimpeller, and a' rnembr having a conical diameter substantially midway offlthddiameters whereby the vanes are; narrower at theirihner ends. i j i X l 2) In a booster pum oi the character I described, a pump casing, an impellerffvanes l on, andradiating outwardly fiomfithe rotating ,axis

of the inner and odter ndsof the vanes, and i said vanes being beveled fromthe throat diameter inward,,wherehy the taper of the throat and the loevel of, the vanes are substantially continuations of each other. i l

3. In a fuel system, 'aiueltankanda booster pump of the,charaeterwdescribed, comprising, a

pump casing, a fiatdisc impeller; vanes onysaid impeller defining therewith open endedfluid flow passages, and a throatjmemberhaying one side immediately adjacent said vanes and the other side in contactwith the fuje'linsai'd tank, said i throat having, a diameter onthe1vane side inter I said impeller mediate the inside and outside diameters of the 3 vanes tofexpose arr-appreciable length of: the

vanes effective for beating out bubblesci gas,

or vapor from the fuel, but flaring to a larger diameter onthe tankside.

4. In a fue1, system, a fuel tankand a booster l Dumpof the, character descri d om n pumpcasing, an impellentapered vanes on said appreciable length beating out bubbles fuel; l I v H 1 a 8; A;. booster pump fdrattachment toanhn- 1 derside' of aiuel tankfsetid pump comprising an impeller dis c having'radially extending vanes on i the inlet faceofljsaid disc, said vanes being raid V peredbatftheirf inner ends toward said disc face and with their inner and outer en'ds lying in circles;concentric with the disc axis; and a plate qverlying saidimpeller dnthdtank side with its loweriaceqin closely spaced relation to'said vanes W iallowl throat-converging toward i c 1 define a circular opening of s? 'ediatel thje diameters of said cir and having; a

diameter interm clcs. y

pered; at their inner ends, toward said disc face overlyingsaid impeller on the tank side with its lower face in closely spacedrelation to said vanes and having a shallowlthroat convergingtjoward' said impeller to define a circular opening of a impeller, and a flared throat member havingone end adjacent said vanes and its other end in 9 contact with the fuel" in said tank, said throat having adiam'eter on the vane side substantially midway of the diameters of the inner and outer ends of the vanespfibut flaring to alarger diam-. l

eter on the tank side, the flare of the throat and the taper ofjthe vanes beingdsubstantial continuations of each other. 3 1 i 5.111 a fuel system for aircraft; a fuel tank,

a centrifugalpump secured tothe outside of said larger diameter on the tank side, andsaid vanes r beingtbevele d from a point intermediate their ends inward, whereby saidfvanes are narrower at their inner ends.

tank, said pump comprising, a pump casing, an impeller, vanes on said-impeller, and a threat member having one side adjacent saidvanes and i diameter intermediate the-diameters of saidcircles, the convergency of said throat and the taper of said vanes being'approximately continuations of each other.

.10. In combination Withaloweror side wall)" oi ,afuel tank,a booster pumpco'mprislng a cas, ing secured to said wall and about an opening formed therein, a driven impeller mounted with its axis perpendicular to said wall, said impeller havine a ir larflangeuwith upstanding ribs g radiating; out from a circlenear said axis, and

a plate mounted in said: tank wall opening 'so as to overlie and be closely'spaced from said ribs and having a shallow throat converging from said tank toward said axis to define an (opening of 'GQInfa fuel system for aircraft; a r el tank,

a centrifugal pump secured to theoutside of said tank, said pump' comprising, a, pump casing, an impeller, vanes on said impeller, andv a shallow th oat memberhaving one side facing said vanes and theotherside facing the fuel in said tank, the

throat in said member having a diameter on the vane side substantiallymidwaypf the insideand outside diameters of the vanes but flaring to a larger diameter onfthe tank side, and said vanes being tapered from thepoint adjacent the i 1 vanesareinarrower at the inner ends. i

throat diameter to their inner ends, whereby said 7, A booster pumpfor attachment ttisf ma H vanes extending outwardly from the axis of'- said having openiinner and outerends', and a member, overlying and spaced from saidimpeller on the tank side in closely spaced relation to tank, said pump comprising an impeller having pump portion in closely spaced relation a substantially greater diameter than the circle defined by the inner ends of said ribs.

11. A pump and motor unit comprising a mo tor, a a casing therearound L having an open mouthed outwardly flanged head portion defining apump' volute chamber and a central passage way, amotor shaft,,extending-from the motor through said passagewayya pump impeller! on said shaft arranged to impel fluidin the open mouth of said head portionintothe volute chamher, a throat ring in the mouthof the head per H tion overlying the volute chamber and defining aninlet to the impeller, and saidflange of the i head portionadaptedto beattachedto the wall a of a tank to: fixedly connect the entire unit to a ta nk. v I 1 i,

12. A device for dischargingffully liquid ma terial, such asvolatile fuel, fromasource of lin ,uid material, which comprises a pump having a i portion defining, a relatively large inlet throat communicating withfsaid source, an impeller assembly adjacent said pump portion, vane portions on the impeller assembly underlapping said fining wallsof open ended liquid flow pu ping 1 channels, and: additional vane portionslof ap1- preciable lengthen the impeller assembly in open communication with the source of liquid and adjacent to and in communication withithe'inlet p pyrqr attachment toankunl dersidey-of a fuel, tank; said pump comprising an impellerdischaving radially extending vaneson a the inlet face offlsaid ldisc said vanesheing ta- 4 a th oat or said ump ortion in the path of liquid how to the pumping channels efi'ective for acting it becomes confined .in the channels toagitatethe material and beat on the liquid material before outbubbles of gas and vapor therefrom.

- 13. ,A devicefor discharging fully liquid ma- I terialQ-such as volatile gasoline; from asource of liquid material, which comprises a pump hav- '-'ing a portion defining a relatively large inlet throat communicating with said source, an impellzr 'assemblradjacent said pump portion including a disk spanning the inlettopening of the I "throat and funderlapping 'said pumplportion around the peripherythereof, vane portions on the outer peripheral porti'on of the disk undergas and vapor therefrom, whereby said channels discharge fully liquid material.

'14. A device'adapted for discharging fully liquid material, such as volatile fuel, from a source lapping said pump portion in closely spaced relation and defining withthe diskand pump .por-.

tion open-ended liquid flow pumping channels, and, additional vane portions of appreciable length on'the lmpeller'assembly in open communication with the source :of liquid and closely adjacent toa'ndln communication with the inlet throat inthe path of liquid flow to the pumping channels effective 2 for. actin'g'on the liquid material. beforeit becomes confined in the channels to agitate'the materialand beat out bubbles of of liquidmaterial,- which comprises a pump having a pump chamber and a relatively large inlet throat communicating with said source, an impeller having vanes for pumping liquid from the and for agitating before it becomes confined in the pumping chan- I nels to beat out bubbles of gas and vapor therefrom.

, RUSSELL R. CURTIS. 

